There is considerable concern about the amount of space debris in orbit around the Earth. Even very small debris objects can cause significant damage to other objects in space as relative velocities in orbit can reach many kilometres per second. Some of the space debris orbiting the Earth includes large objects, ranging from inactive satellites to expended rocket booster stages. Objects such as those mentioned can cause serious damage to a spacecraft on collision and be a plentiful source of further smaller debris fragments in the event of a collision with a space vehicle or other debris objects. The amount of space debris already in orbit is thought to pose a threat to the continued use of certain orbital bands, such as those within the Low Earth Orbit (LEO) range used for communication satellites.
Numerous studies have been carried out into the problem of space debris. The main features of these proposals are:                a “chaser” or “servicer” which rendezvous with the target item of space debris;        a docking or capture manoeuvre, followed by a stabilization manoeuvre; and        a de-orbit manoeuvre.        
Such “active debris removal” (ADR) configurations therefore retrieve objects from an orbit using a chaser or service vehicle (typically comprising at least a capture device, propulsion system, and navigation system) which then manipulates the retrieved objects so that they deorbit, for example by burning up in the Earth's atmosphere. To save costs the chaser or service vehicle would be kept in orbit for future missions, however, which therefore makes the deorbit process complex.
These configurations make use of a satellite which hosts the chaser or servicer components. As such, a satellite launch is required before the chaser or servicer components can be deployed. Such missions have proven to cost of the order of several hundred million euros. The required power and fuel consumption for the satellite launch and repeated docking or de-orbit manoeuvres are significant components of the mission costs, together with operation costs. In addition the technical complexity associated with effective docking routines and de-orbit manoeuvres have led to alternative solutions being sought.
One alternative solution proposed in the literature is to use chemical thrusters to provide a braking force to the target, so as to reduce the potential for debris to continue to cause damage via high-velocity collisions. However, these techniques would be extremely problematic due to the high heating from bi-propellant or mono-propellant systems which could melt the target. Cold gas would also be very mass-inefficient. In addition the stand-off distance would be only a few metres which would lead to a high risk of collision between the target and the service vehicle. Therefore such a technique might only be useful for small items of debris. Electric thrusters are an alternative to chemical thrusters, although these are also likely to be expensive.
Another proven solution is the destruction of space debris with a ground-launched missile, rather than its capture. While this technique is simpler, it generally leads to an increase in smaller space debris, particularly following the destruction of large objects at an altitude of over 600 km, and so in some circumstances, this approach may actually worsen the space debris problem.
The present invention aims to provide a non-destructive capture and deorbit technique which is much more cost-efficient than those currently used. The present invention eliminates the use of a host satellite and uses a dedicated launch system as the debris interceptor, configured so as to intercept a target object, rather than destroy it. This configuration leads to a significant cost reduction, and the possibility of multiple active debris removal missions using different launcher/interceptor vehicles.